Heat economizer for small units



S. F. RIZZO HEAT ECONOMIZER- FOR SMALL UNITS April 14, 1959 Filed Nov. 50, 1955 2 Sheets-Sheet 2 lu u Ll] INVENTOR. Salvatore Rlzzo United States Patent HEAT ECONOMIZER FOR SMALL UNITS Salvatore F. Rizzo, Massapequa Park, N.Y., assignor to Home Heating Devices, Inc., New York, N. a corporation of New York Application November 30, 1955, Serial No. 549,995

' 6 Claims. 01. 257-2 This invention relates to improvements in heating devices and heat economizers and the like.

An object of the invention is to provide a novel and improved device which may be attached to or used in connection with a furnace or the like, for extracting heat from the hot gases on the way to the chimney, for use as desired.

Another object of the invention is to provide a novel and improved device which may be installed in the smoke stack of a heating system, so as to allow the hot chimney gases from a furnace to flow through the main casing of the device, while clean air to be warmed is piped through the interior of the main casing by means of interior ducts, thus extracting heat from the hot gases to warm the clean air, the heated air being moved through its own ducts by means of an inducer fan or blower.

A further object of the invention is'to provide a novel and improved heat economizer which reclaims from the flue gases, a large part of the heat contained therein, which would otherwise be wasted up the chimney, and which economizer has novel construction for separating the hot flue gases from the clean air to be warmed or heated in the economizer casing, while at the same time permitting optimum heat extraction without interference with the normal operation of the furnace. I

Still another object of the invention is to provide a novel and improved furnace accessory, whichemploys Waste usual heat from radiators supplied by the regular heating system of the building, while not adding to the heating burden normally loading the furnace.

Still a further object of the invention is to provide a novel and improved heat economizer of the type de scribed, in which there is a main housing through which the flue gases flow, and a separable frame supporting a large number of fresh air ducts or pipes of relatively small diameter to lie across the interior path of the hot flue gases, an inducer fan being used to movethe fresh air through the pipes as to become well heated from the hot gases, the frame with its pipes being readily removable from the main housing for inspection, cleaning, and servicing, without need for special tools or the like, with special interior constructional features for adding to the efficiency of heat extraction by the device as needed.

Another object of the invention is to provide a novel and improved heat economizer of the character described, which is simple in design, inexpensive to manufacture, is readily installed in most smoke pipes for its intended use, and which is eflicient and economical in reclamation of waste heat.

These and other objects and advantages of the invention will become apparent from the following description of a preferred embodiment thereof, as illustrated in the accompanying drawings, forming a part hereof, and in which,

Figure 1 is a perspective view showing the novel and ICC improved heat economizer unit installed in the smoke pipe or flue of a building furnace and chimney.

, Figure 2 is a perspective view showing the heat economizer unit apart from the furnace and chimney, the view showing the device with its main axis in a vertical orientation.

Figure 3 is a sectional elevational schematic view taken substantially on plane 3-3 of Figure 4.

Figure 4 is an exploded view in plan of the device shown in Figure 3, the removable air-tube array being shown removed from the main housing for clarity of illustration.

Figure 5 is a sectional elevational view showing a modified form of the invention, the plane of the view being taken at right angles to the axes of the air-tubes, and showing use of multiple baffles for increasing heat transfer efliciency.

Figure 6 is a right side elevational view of the device shown in Figure 5, the view being partly sectional vertically to illustrate the construction.

' Figure 7 is a sectional elevational detail view of one of the heating tubes for air conduction, taken substantially on plane 7-7 of Figure 8, showing use of spiral or twisted air guiding core for enhancing heat transfer efiiciency.

Figure 8 is a left end elevational view of the parts shown in Figure 7, in fragment.

Figure 9 is a transverse sectional elevational detail view taken substantially on plane 9--9 of Figure 10, and showing a modified form of the invention, with reference to the by-pass area.

Figure 10 is a left side elevational view of the device shown in Figure 9, the view being partly broken out to show the interior construction.

Figure 11 is a plan view similar to Figure 4, but showing the parts in assembled relation, the view being broken out partly for illustration of the interior construction.

In connection with the use of furnaces for heating buildings, by means of fuel such as coal, oil, or the like, it is found that a large amount of the heat energy available from the combustion of the fuel is wasted in the hot gases which pass up the chimney. Thus it has been found in some installations, that the temperature in the smoke pipe leading out of the furnace and to the chimney, is as great as about 750 degrees Fahrenheit, indicating that considerable waste heat is present in the flue gases. The present device is intended for the purpose of reclaiming or saving some of this heat, by abstracting it from the hot flue gases and using it to heat some portion of the build ing, directly or indirectly, thus complementing the usual heating elfort of the radiators of the heating system, and thus increasing the total heating efliciency of the system.

In order to do this, it must be understood that care must be taken not to place in the path of the hot flue gases, an intensely cold massive body, such as a hot water jacket, which might cool the flue gases unduly, and interfere with normal chimney operation, and hence with the operation of the boiler itself. Further, if such an undue cold load is placed in contact with the hot gases, there would be a tendency to form large carbon deposits, soot and the like, which'would defeat the purpose of the device. Accordingly, the present invention provides means for abstracting waste heat from the flue gases, without overcooling them, so that optimum heat transfer is obtained. This is accomplished by interposing in the path of the hot flue gases, a large number of relatively small diameter fresh air heating pipes or ducts, through which air to be heated is forced by means of a fan or blower, so that the thus heated air, resulting from contact of the hot flue gases with the pipes, is available either for piping to some room of the building, or for heating the basement or furnace room, or otherwise as desired.

In order to understand clearly the nature of the invention, and the best means for carrying it out, reference may now be had to the drawings, in which like numerals denote similar parts throughout the several views.

As shown, there is a furnace generally indicated at 10 which is connected to the chimney 12 by any duct means, such as the'smoke pipe 14, suitable bends being provided as at 16 to allow the riser 18 to interconnect with the horizontal portion 20 of the pipe 14. As the 'hot gases arc flowing from the furnace 10 to the chimney 12, at a temperature in the vicinity of about 750 degrees Fahrenheit, or thereabouts, the present device is interposed as at a break 22 in thesmoke pipe or flue, for abstracting a large part of this waste heat from the gases, so that it may be expected that the temperature of the gases leaving-the device 24 maybe reduced to about 350 degrees Fahrenheit, or thereabouts.

In order-to accomplish this, thedevice 24 is provided with "-a'main housing 26, formed with side walls :28, 30 and 32, interconnected at edges 34 and 36, to form "a chamber at 38, with end walls 40 and 42 closing -the chamber 38 at the top and bottom as seen in Figure-2, or at the entrance and exit ends as seen in Figure 1. It

.is thus apparent that the chamber 38 is open at one'side 44, -so that a separate closure must be provided thereat. For this purpose there is provided a removable side 'wall or door 46 which fits over the openingthus formed in the main chamber 38, and is equipped with a handle 48 extending from door, to permit readily Zpulling the door open or closing same.

As seen best in Figure 4, the drawer door has a pair of side walls 52 and 54 secured at their inwardly dis posed edges to a rear wall 56, atapered air inlet duct being formed as at 58 to receive air blown therein by the outlet 60 'of the centrifugalfan housing 62,'-which pulls air in through its airinduction opening '64," from any suitable source, such as through duct 66 or the likeyto bewarmed in" the device. The fan .housing' '62 is provided with a suitable fan inside the housing, which is driven-by means of a motor 68 connected by wires to a source of electric power.

It is thus apparent that the fan 62 is capable of drawing air-to be heated, from any suitable sourcefsuch as the basement, furnace room, garage, storage room, or other space, moving itthrough-the main housing '38, and after it is heated, blowing it back, thr'o'ughsui-table ducts, if removed from the furnace room, to heat said remote rooms. To'extract heatfrom the furnace-gases which enter the device 24 at 70,and leave it at 72, there are ptov'idedanumber of heating tubes 74, heading into the walls-46 and 56 respectively, and guided by the' taper ducts orconnectors, 58, it being observed that the" air is thus blown through the heat absorbing tubes 74 which connection of the flue with the fresh air in the ducts 74.

lie acrossthe'path' of the hot flue gases, without actual contact of the fresh air in the tubes 74 with the-hot flue gases, 'As' 'aresult, the air in the tubes 74-becomes heated upto 'a considerable temperature, as "it :isblown'by' fan 62 through'the tubes 74, and is then blown out through the openings 80 through which the tubes 74' pass out of the header wall' 46, and thus through any'suitabl'e-delivery duct or pipe 82'connected therewith for deliv'ery of the heated air toanother room, garage, attic, or the like by means of such'duct 82, although, if the heatis to be used in the furnace room or basement,"then such duct 82 will normally not be needed. However, where the fresh heated air 'is to be piped to some distant room, garage, greenhouse, or the like, then ductwork-will 'be considered necessary so that there will be'no interfer- 'ence with the general heating system 'of "the house or building.

The interspacing'of the-air tubes 74 is so'chosen'as to provideminimal air stream interference-in regard to the moving hotgases of the furnace output 10, yet perfor optimum heat transfer. -flow of air tobe heated is arranged so that there is mitting optimumabst'raction'of heat from-the-hotgases I Thus there is permitted a variation in the air speed of movement by fan 62, regardless of the speed of movement of the hot air gases in the flue 14.

Looking at Figures 1 and 2, it is seen that there is quite a large number of such fresh air tubes 74 carried by and opening at one end upon the end wall 46, such tubes being relatively small in diameter, yet sufiiciently spaced to permit free passage of fiue gases therepast. As shown in Figure 3, however, in view of the large number of such fresh air tubes 74 shown, "and due to unusual temperature and condensation conditions, after a substantial period of time, there may be some formation of soot or carbonon thetubes 74. In this event, there is provided means for passage of the hot fiuegases therepast nevertheless, through a by-pass chamber 88 defined by an end casing 80.

Thus normally any hot flue gases will flow in the direction -of arrows 82 shown in Figure 3, over the outside of the tubes 74, andfrom arrow 84 to arrow 86 and thence to thechimney. However, should any of the passages between the pipes 74 become obstructed, 'then there is provided a bypasschamber 88, through which the obstructed gases may flow in the direction of arrows 90, as seen in Figure 3. The bypass chamber 88 is provided with walls 92 and end wall 96, formed to allow entry of-fan outlet duct 60 therethrough. While the hot flue gases may normally flow in the direction of arrows 82 in Figure 3, itisseenthattheymay also flow in the direction of-arrows through the bypass chamber 88 when needed. To aid in extracting hot temperatures from the flue gases, 1, provide a number of fins or vanes 94, which extendout of the fan outlet 60, thus permitting the hot fluegases which flow in the direction of arrows 90 in Figure.3,to add to the heatconveyed-from the gases to the fresh air in-the pipes in the bypass 88. Thus there is amarkedaddition to the ultimate efliciencyof heat transfer in view of this added fin area in the bypass 88.

It'must be understood that where the bypass 88 is employed, asin Figure 3, such areashould be kept free of obstruction to avoid blockage with soot and carbon deposits, andfor such purpose, there is provided a differential offset positioning of the various discs 94 seen in the'views' in the bypass. Thus as seen in Figures 9 and 10, the heat extraction discs 94a of the bypass may be adjustably turnable so as to be eccentrically disposed alternatively,'so that one set as :at 94a is vertically offset fromvcenter of the pipe 60, while the other set as at 94b is vertically downwardly ofiset as in Figures 9 and 10. This permits free movement of flue gases at all times through the device from inlet pipe 70 to outlet pipe 72, either directly through in the directions of arrows 82,-or through the bypass in the directionofarrows 90. At the same time, there is a maximumintermixture of hot flue ,gas with surface of the fins shown, and thus transfer of heat therebetween, due tothe multifarious paths ofmovement of the gases.

'Figures 5 and 6 show another modified form of the invention, in which baffie walls are employed for further enhancing the heat interchange while in the main housing. Here there isa number of plane bafiies or walls a, 100band 100e, the bafiles 100a and 100a extending-out of the wall 26a, while thebaffle 100]; extends out of the wall 28a, substantially midway therebetween, their inner edges 100aa, 100bb, and 100cc being situated-as shown in the views, to force the hot flue gases to flow in the undulating path indicated by the arrows, Figure 6 shows how the counterfiow movement, with optimum heat transfer, the cool air being drawn in by the fan 62 and moving in the direction of the arrows to the fresh air outlet duct 112 which may be coupled by suitable piping to -a room tobeheated thereby, such as a garage, store-room, attic, etc, or basement.

To permit of easy assembly of the main housing 26 to the various sections of the smoke pipe or flue 14, there are provided a pair of couplings 114 and 116 or adapters, which are of a sufiicient inside diameter at their larger ends to fit over the smoke inlet 93 and smoke outlet 95, as seen in Figure 3, and to interfit with the smoke pipes 20 and 14 respectively in the manner of Figure 1, as needed, being reduced accordingly thereat. It is understood that the couplings 114 and 116 may also be made eccentric, so as to interfit conveniently with offset sections of the smoke pipe as found to exist, by turning them about their axes for such purpose.

Figures 7 and 8 show how further enhancement may be obtained of the heat transfer by means of an inducement of radial outcasting of the fresh air which flows through the fresh air pipes 74. This is accomplished by means of an insert or core 120, which may be formed of a bar of metal which is twisted spirally about its axis, that is, about the axis of the tube 74, being supported therein centrally in any suitable manner, as by means of ribs 122 radially interconnecting the bar 120 with the tube 74. By use of the spirally wound ribbon 120, the fastly moving air through ducts 74, is cast outwardly toward and in contact with the tube 74 itself, thus aiding in heat transfer to a greater extent than otherwise, since there is no relatively cold air core in the tube.

Although the invention has been described in specific terms, it will be understood that various changes may be made in size, shape, materials and arrangement without departing from the spirit and scope of the invention as claimed. Figure 1 shows how the thermostatic switch 137 is mounted right on the main housing 26 by means of tube 139 which carries the thermostatic bi-metal element inside housing 26, wires 141 connecting the switch and blower fan 68 to the power lines, to turn on and off the fan, responsive to temperature in housing 26. The wall 46 with its bank of heating tubes 74 is slidable on ribs and grooves jointly carried as at 135 by the wall 46 and side walls like 32 of housing 26, and a latch is shown at 133 for locking wall 46 in place. A cleanout plug 131 permits insertion of vacuum and blowing means to clean out the interior as needed without disassembly.

I claim:

1. A heat economizer comprising a main housing, a first furnace connection port for connecting said housing to a furnace to receive hot flue gases therefrom to flow inside said main housing, said housing having a main chamber to receive said gases, a chimney connection outlet port for connecting said main housing chamber to a chimney or the like, a first wall in said main housing having a fresh air discharge opening formed therein, a second removably supported wall in said main housing opposite said first wall and having a plurality of fresh air intake openings formed therein, a plurality of fresh air conducting and heating tubes carried by said second wall and connected at their first ends with said fresh air intake openings to receive fresh air to be heated therethrough, said array of second wall and its plurality of fresh air conducting and heating tubes being constructed and arranged for insertion of said heating tubes into said main housing chamber to lie across the path of said hot fiue gases, while, when so inserted, said heating tubes have their second ends registered with said fresh air discharge opening in said first Wall of said housing, for discharging heated air therethrough, impelling means disposed in the path of flow of said fresh air for inducing its flow through said heating tubes, and handle means constructed and arranged for inserting and removing said movable wall and its bank of heating tubes.

2. The construction according to claim 1, wherein there is a bypass housing forming an extension of said main housing chamber and connected therewith, so that excessive flue gas flow from the furnace is bypassed through said bypass housing around said bank of heating tubes and avoiding them, whereby suflicient total flow path is always present in the event of blockage of the path over and around said heating tubes.

3. The construction according to claim 2, wherein in said bypass housing there is an extension duct connecting said impeller fan with said bank of heating tubes, and adjustably positionable heat absorbing fin means carried by said extension duct for absorbing heat from the bypassed flue gases to heat said fresh air.

4. The construction according to claim 2, wherein in said bypass housing there is an extension duct connecting said impeller fan with said bank of heating tubes, and heat absorbing fins carried by said extension duct for absorbing heat from said bypassed flue gases to heat said fresh air, said fins being eccentrically mounted on said extension duct, and adjustably turnable, so that they may be alternately variably oriented angularly, to provide optimum free passage for flue gases while avoiding stoppage due to soot gathering on said fins.

5. The construction according to claim 1, wherein there is a thermally responsive switch interposed in the circuit of said impeller fan means for opening and closing said circuit, said switch including a thermally responsive switching element extending inside said main chamber for reacting to the temperature therein, whereby upon its reaching a predetermined temperature, said switch closes, turning on said impeller fan to draw heat from said hot flue gases.

6. The construction according to claim 1, wherein there is a cleanout port formed through said main housing, to provide access to the interior of said main chamber, closure means normally closing said port, and open able at a low elevation thereof to allow insertion through said port of both blowing and suction apparatus for cleaning said main chamber, and said contents thereof without need for removing said heating tubes.

References Cited in the file of this patent UNITED STATES PATENTS 518,864 Sheppard Apr. 24, 1894 1,292,615 Koenig Ian. 28, 1929 2,032,553 Spoelstra Mar. 3, 1936 2,104,804 Hill Jan. 11, 1938 2,147,658 Lepick Feb. 21, 1939 2,575,894 Shireman Nov. 20, 1951 2,693,941 Bystrom Nov. 9, 1954 

